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At large charge input (high energy photons as well as high count rate) some saturation of the gain is arising in the PSPC. The fall-off in the signal amplification as a function of event amplitude has been modeled using spectral calibration data (cf. Eq. (F.6)) . At present the rate gain effect is not taken into account.
The offset values 
for 
135, 146, and 103
are 
89.2, 96.1, and 69.1, respectively.
Below these values thresholds gain saturation is negligible.
According to
Chap. 3
the rate gain effect can be understood in terms of pseudo-continuous
presence of a substantial electron cloud causing a reduction in the
electronic field.
Measurements at the PANTER test facility have shown a drop of
the gain of 1% at E = 1.487keV and 2% at E = 3keV for an
X-ray count rate of 500s 
.
Further investigations were planned.
Figure F.3 shows the PHA channel difference between the non-linearity and gain saturation correction.
Figure F.3: Difference between the channels after gain saturation correction
( 
) and after non-linearity correction ( 
) as function of
according to Eq. (F.6).
The correction effect is shown for three typical gain values
( 
, 135, 146).
Parameters:
] PHA channel of the Al K 
line (BAL )
(from Prescott fit)
SASS source code: package PSPC, bubble CT, subroutine CGS
SASS files: none
Figure F.4: The temporal gain correction factor 
according to Eq.(F.7)
as function of the gain (expressed in terms of the
Al K 
line bin 
).
It is 
,
,
and 
.
